Lecture 9 Notes

Overalleqw conservationofenergyandchangesofstate

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Unformatted text preview: id = ‐911 J exothermic Work occurs as the sample expands or contracts. Overall: ΔE = q + w Conservation of Energy and Changes of State A system does 50.2 J of work on its surroundings and there is a simultaneous 90.1 J heat transfer from the surroundings to the system. What is ΔEsystem? Work done on the surroundings by the system Heat transfers from the surroundings to the system +90.1 J wsystem = ‐50.2 J qsystem = (qsurroundings = +911 J) ΔEsystem = qsystem + wsystem ΔEliquid = ‐911J ΔEsystem = ‐50.2 J +90.1 J = +39.9 J Enthalpy: Heat Transfer at Constant P During freezing (or melting) ΔE = qV • subscript V shows fixed V • work requires...
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